Method for producing a toothbrush

ABSTRACT

The invention relates to a method for producing a toothbrush with a solid handle ( 2 ) having a large cross-section. Either one section only of the material provided for producing the handle ( 2 ) is injected into a first cavity ( 8 ) and the remaining part of said material is injected in one or more portions into an additional cavity ( 12 ) and brought into contact with at least one of the parts that have already been injected, or the material provided for producing the handle ( 2 ) is fully injected into the first cavity and subsequently displaced into a cooling cavity in order to cool and harden. The method enables short injecting intervals.

[0001] The invention relates to a method for producing a toothbrush inaccordance with the preamble of claim 1.

[0002] WO-A-94/05183 discloses a method for producing a toothbrushconsisting of two different material components, in which method, in afirst step, the main body of the toothbrush is injected from a firstmaterial component, for which purpose a first cavity is provided.Thereafter, in a second cavity, a further material component, forexample an elastic and/or nonslip material, is injected onto variousparts of the main body. The main body has a relatively narrow crosssection both in its area supporting the bristles and also in its handlearea.

[0003] In order to improve the grip of toothbrushes and to permitcomfortable handling, it is advantageous to make the toothbrushrelatively solid in its handle area, i.e. to give the handle arelatively large cross section. However, this kind of handle designentails a number of disadvantages from the point of view of productiontechnology. Not only is more material used as a result of the greatervolume of the handle; the injection time and cooling time are alsohugely increased by the greater mass, and the injection-molding processis thus prolonged (longer molding time). In addition, such handle partswith a relatively large cross section have a tendency to cavitation(i.e. formation of air bubbles) which are visible in handles made of atransparent material and detract from the esthetic effect of thetoothbrush.

[0004] The object of the present invention is to propose a method of thetype mentioned at the outset which guarantees short injection intervalswhen producing a toothbrush with a solid handle of large cross section.

[0005] According to the invention, this object is achieved by a methodwith the features of claim 1.

[0006] The invention is explained in greater detail below with referenceto the drawing.

[0007] Three variants of the method according to the invention areillustrated in the drawing and are described in greater detail below.

[0008] In the drawing, which is purely diagrammatic:

[0009] FIGS. 1 to 3 show a first method variant in three steps;

[0010]FIG. 4 shows in a side view, and partially in cross section, atoothbrush produced according to the method steps in FIGS. 1 to 3;

[0011]FIG. 5 shows a plan view of part of an injection mold for thefirst method variant;

[0012]FIGS. 6 and 7 show a second method variant in two steps;

[0013]FIG. 8 shows in a side view, and partially in cross section, atoothbrush produced according to the method steps in FIGS. 6 and 7;

[0014]FIG. 9 shows a plan view of part of an injection mold for thesecond method variant; and

[0015]FIG. 10 shows a plan view of part of an injection mold for a thirdmethod variant.

[0016] To produce a toothbrush 1 which is shown in FIG. 4 and whosehandle 2 has a larger cross section than the front head part 3 providedfor securing the bristles or tufts, an inner part 4 of the handle 2 isfirst prepared in a first step shown in FIG. 1. For this purpose, afirst portion of the first material component provided for the handle 2(and if appropriate also for the head part 3) is injected into a firstcavity a formed between two parts 5, 6 of an injection mold 7. The firstinjection point for the first material component delivered from a firstunit A1 is indicated by AP1 in FIG. 1, while the injection channel orinjection nozzle provided for this is indicated by 9.

[0017] As can be seen from FIG. 5, the injection mold 7 is provided forthe production of a plurality of toothbrushes 1, if appropriate eighttooth brushes 1. After partial cooling and hardening (as soon assufficient inherent stability is achieved), the inner parts 4 injectedin the first step according to FIG. 1 are transferred in each case intoa second cavity 12, shown in FIG. 2, using a generally known transfersystem (not shown in the drawing), for example a so-called internalhandling system arranged on the injection-molding tool, an externalrotary or linear handling system, or robots. This first transfer isindicated symbolically with an arrow U1 in FIG. 5.

[0018] The inner part 4 can have support knobs (not shown in FIG. 1)which protrude in the radial direction and by means of which the innerpart 4 is supported on the wall of the second cavity 12, in order to beheld centrally there.

[0019] In a second step shown in FIG. 2, a second portion, ifappropriate the remaining portion, of the first material component isinjected into the second cavity 12 via an injection channel or aninjection nozzle 13. The second injection point AP2 for the firstplastic component is offset in relation to the first injection gate AP1,viewed in the longitudinal direction of the toothbrush to be produced.The second portion of the first material component comes into directcontact with the first portion; in the illustrative embodiment shown,material is injected around the inner part 4, the handle 2 acquires thedesired solid shape in its rear area, and the front head part 3 ofnarrower cross section is also obtained. Thus, a main body of thetoothbrush 1 is formed which consists of the first material componentand is indicated by 10 in FIGS. 2 and 5. To inject both portions of thefirst material component, only one unit A1 is preferably used, as isindicated in FIGS. 1 and 2. However, the two portions of the samematerial could also be injected from two different units and could forexample have different colors.

[0020] In the method variant according to FIGS. 1 to 5, in a third step,a further material component, for example a material which is moreelastically resilient compared to the first material component, e.g. athermoplastic elastomer (TPE), is finally injected around the front areaof the handle 2. For this purpose, the main body 10 consisting of thefirst material component is transferred into a third cavity 16 of theinjection mold 7 after the second portion has cooled and hardened, inwhich case once again the second transfer of all eight main bodies 10,indicated by the arrow U2 in FIG. 5, is effected by means of a suctiontool (not shown).

[0021] According to FIG. 3, the second material component is injectedinto the third cavity 16 from a further unit A2 via an injection channelor injection nozzle 17 at a third injection point AP3, material beinginjected around a front part 2 a (FIGS. 2 and 3) of the handle 2 and akind of coating thus being formed over part of the length of the handle.Such a grip part 20 can contribute, for example, to a furtherimprovement in the gripping of the toothbrush 1. It is of coursepossible to add further material components into further cavities.

[0022]FIGS. 6, 7 and 9 show a further method variant for producing atoothbrush 1′ which is shown in FIG. 8 and which once again has a fronthead part 3 and a handle 2 of greater cross section compared to thelatter. In a first step in this variant, according to FIG. 6, the headpart 3, a front part 2 a of the handle 2, and a part 2 b of the rearpart of the handle with increased cross section, are injection-moldedfrom a first material component and together form a main body 30 of thetoothbrush 1′. The first cavity provided for this purpose and formedbetween two parts 25, 26 of an injection mold 27 is indicated by 28 inFIG. 6. This first cavity 28 is designed in such a way that the part 2 bof the handle 2 has an upper injection surface 24 extending at aninclination relative to the longitudinal direction of the toothbrush 1′to be produced; the injection surface 24 could of course extend inanother direction. At an injection point AP1, a first portion of thefirst material component from a first unit A1 is injected into the firstcavity 28 via an injection channel or injection nozzle 29. As can beseen from FIG. 9, a number of main bodies 30, possibly eight mainbodies, are once again produced in one injection mold 27 and, afterpartial cooling and hardening, are transferred into a second cavity 32shown in FIG. 2 by means of a transfer system (not shown). This transferis indicated with an arrow U1 in FIG. 9.

[0023] In a second step shown in FIG. 7, the second, remaining portionof the first material component is injected via an injection channel oran injection nozzle 33, preferably from the same unit A1 as the firstportion, into the second cavity 32 at a rear, second injection point AP2which lies behind the injection surface 24 of the main body 30 locatedin the cavity 32. Here too, however, an additional unit could be madeavailable for the second portion. The remaining part 2 c (FIG. 7) of thehandle 2 is formed by the second portion of the first material componentinjected onto the injection surface 24 of the cooled handle part 2 b. Inthis variant, the main body 30 is designed in such a way that the spacein the second cavity 32 provided for injecting this second portion (orfor forming the remaining handle part 2 c) is separated from a space ofthe second cavity 32 provided for the injection of a second secondmaterial component surrounding the front handle part 2 a, thisseparation being effected by a peripheral surface 34 of the insertedmain body 30 which is located at the transition between the front part 2a and the part 2 b of the handle 2 provided with the injection surface24. Thus, simultaneous with the injection of the second, remainingportion of the first material component, it is also possible to injectthe second material component, specifically from another unit A2, at athird injection point AP3, via an injection channel (or injectionnozzle) 37 opening into the second cavity 32. Here too, in order toimprove its grip, the handle 2 is provided with the grip part 20consisting, for example, of an elastically more resilient materialcomponent. If necessary, the injection of the first and second materialcomponent could take place sequentially.

[0024] Accordingly, in the second method variant according to FIGS. 6, 7and 9 (in contrast to the first variant according to FIGS. 1 to 3 andFIG. 5), only two cavities 28, 32 are needed for each toothbrush 1′, andonly one transfer U1 is required.

[0025] Both in the first method variant and in the second methodvariant, by dividing the injection-molding of the handle 2 of thickenedcross section into two operating steps, i.e. by injection-molding thesame material in two portions, the injection time and the cooling timeare substantially reduced, i.e. shorter injection intervals arepermitted, and in addition the formation of cavities is avoided. Thelast-mentioned advantage is of particular importance in transparent ortranslucent handles. The separating lines, or in the case of transparentmaterial the separating surfaces, between the handle parts injected inthe individual portions are barely visible. Of course, these handleparts (and the cavities required for them) could have a different formthan that represented and described in the illustrative embodimentsaccording to FIGS. 1 to 5 and FIGS. 6 to 9. It would also be entirelypossible for the handle of thickened cross section to be injected inmore than two portions, and to provide an additional cavity for eachfurther portion.

[0026] The production of a two-component toothbrush 1, 1′ has beendescribed with reference to FIGS. 1 to 5 and FIGS. 6 to 9, respectively.A one-component toothbrush, i.e. a toothbrush consisting of a singlematerial component, could of course also be injection-molded in two ormore portions according to the invention.

[0027] A two-component toothbrush could also be of a quite differentconfiguration than that shown in FIG. 4 or 8. For example, the head part3 could be made from another material component than the handle 2. Inthis case, the material component provided for producing the handle 2 ofgreater thickness than the head part 3 could advantageously be injectedin two portions of approximately the same size.

[0028] In a multi-component toothbrush, however, a number of materialcomponents can according to the invention also be divided into two ormore portions which are injected sequentially. For each component whichis divided up, an additional cavity per portion is of course required.

[0029] A further method variant for producing a toothbrush, ifappropriate once again a two-component toothbrush 1″, is indicated inFIG. 10. In a first step, a main body 40 of this toothbrush 1″, whichhas a head part 3 and a handle 2 of larger cross section, is produced byinjecting a first material component into a first cavity 41 of aninjection mold 42, the first material component being completelyinjected into the first cavity 41 in this variant. Accordingly, as soonas sufficient inherent stability is achieved after partial cooling andhardening, the main body 40 is transferred into a cooling cavity 43 bymeans of a suction tool (not shown), which transfer is indicated with anarrow U1 in FIG. 10. In the cooling cavity 43, which is not providedwith any injection point or injection channel, further cooling andhardening of the main body 40, in particular of its solid handle 2,takes place until there is no risk of deformation when, in a furtherstep, the main body 40 is transferred into a further cavity 44 (seearrow U2 in FIG. 10) into which a second and for example moreresiliently elastic material component is injected in order to form thegrip part 20. This variant too permits short injection intervals bymeans of the transfer U1 of the main body 40 into the cooling cavity 43.

[0030]FIG. 10 again shows by way of example an injection mold 42provided for the simultaneous production of 8 toothbrushes. Of course,in all the variants, other mold sizes having another number of cavities(e.g. with 16, or 24 cavities per operating step) are conceivable.

[0031] A wide variety of plastics can be used as suitable materialcomponents, and these can be at least partially transparent materials,for example styrene-acrylonitrile, polyester, polystyrene, polyamides,polycarbonates, polymethylmethacrylate or others. Examples of opaquematerials that can be used are polypropylene, thermoplastic elastomersor polyethylene.

1. A method for producing a toothbrush from at least one materialcomponent, comprising injecting the material component into a cavity (8;12; 16; 28; 32; 41; 44) of an injection mold (7; 27; 42), characterizedin that either only one portion of the material component provided forforming the handle (2) is injected into a first cavity (8; 28) and theremaining part of this material component is injected in one or morefurther portions into in each case a further cavity (12; 32) and thusbrought into contact with at least one of the portions that have alreadybeen injected, or the material component injected completely into thefirst cavity is subsequently transferred into a cooling cavity in orderto cool and harden.
 2. The method as claimed in claim 1, characterizedin that the material component provided for injection-molding in two ormore portions is delivered to the individual cavities (8, 12; 28, 32)from the same unit (A1).
 3. The method as claimed in claim 1,characterized in that the material component provided forinjection-molding in two or more portions is delivered to the individualcavities (8, 12; 28, 32) from different units.
 4. The method as claimedin one of claims 1 through 3, characterized in that, when injecting asecond portion of the material component provided for forming the handle(2) into a second cavity (12), this is injected around a part (4)injected from the first portion of this material component.
 5. Themethod as claimed in one of claims 1 through 3, characterized in that,when injection-molding a second portion of the material componentprovided for forming the handle (2), this portion is injected into asecond cavity (32) onto an injection surface (24) of a part (30)injected from the first portion of this material component.
 6. Themethod as claimed in one of claims 1 through 5, characterized in that,when injection-molding a second portion of the material componentprovided for forming the handle (2), a second material component issimultaneously injected into the second cavity (32), in which case thatpart of the second cavity (32) provided for the second portion of thefirst material component is separated from that part of said cavity (32)provided for the second material component by the part (30) produced inthe first portion or in the first cavity (28).
 7. The method as claimedin one of claims 1 through 6, characterized in that the materialcomponent provided for forming the handle (2) is injected in twoportions of approximately equal size.
 8. The method as claimed in one ofclaims 1 through 6, characterized in that at least one portion of thematerial component provided for forming the handle (2) is at leastpartially transparent or translucent.
 9. The method as claimed in claim3, characterized in that the individual portions of the materialcomponent provided for forming the handle (2) are of different color.10. The method as claimed in one of claims 1 through 9, characterized inthat a number of toothbrushes (1; 1′; 1″) are produced simultaneously ina corresponding number of cavities (S, 12, 16; 28, 32; 41, 43, 44) inone injection mold (7; 27; 42).
 11. A toothbrush produced in the methodas claimed in one of claims 1 through 10.